Fetch Decode Execute Cycle (Immediate Addressing)

[@tallsamurai7861]

Absolutely stunning work. Thanks for the precise explanations!

[@acluster3411]

So nicely done!

[@blochbuster]

This is a very nice and clear explanation thank you!

[@johnphilipjones]

Thank you for your comment Phil

[@martint5340]

Brilliant

[@ibrahimtayyem9260]

Thanks a lot :)

[@ixi9]

brilliant!

[@andrewskyworker]

hello can you explain what is buffer register and IR register and why they need it?

[@johnphilipjones]

Within a computer system and CPU many binary patterns move from one location to another as small pulses of electricity. In any one second millions of these patterns move around. Each pattern only exists on the paths (the bus system) between components for an extremely short period of time. These patterns can be ‘captured’ for longer storage in registers. So an instruction stored in memory as voltage levels is moved via the bus system (as electrical pulses) and stored in the IR register as voltage levels do it can then feed the input of the decoder (when the decoded ready).

[@Noblesse820]

one question : so the op code gets from memory via data bus to BR then to IR ,the operand gets from memory via data bus to BR then to register A does the processor know that it has to put the op code to IR and the operand to A ?

[@johnphilipjones]

Hello Youssef, When a program starts executing (e.g. when you switch on the computer) the CPU assumes that the first fetch is the op code and this is put in the IR (via the data bus and BR). What happens next depends on what the op code defines. If the instruction is a one byte instruction (e.g. increment a register) then the next fetch will also be an op code so this will be put in the IR. However, if the instruction is not a one byte instruction then what is fetched next is the operand and this is not sent to the IR it can for example be sent to register A (i.e.a load Register A instruction). So based on the nature of the instruction (i.e. the operation as defined by the op code) then the CPU 'knows' what to do next. Look at the next two videos in the Playlist they deal with different types of instructions Regards Phil (John Philip Jones)

[@Noblesse820]

ohh i see now thank you ,it was really helpful .Best regards

[@harisankarl6292]

nice

[@mobilealg8367]

please, can you tel me how do you know that 3C is icremante A, and 3E is LD A ?. Can you give me the instructios table ? thank you so much!

[@johnphilipjones]

Search for the following on Google and it should locate a PDF file of a manual that contains the instruction set. Zilog Z80 instruction set Best wishes Phil

[@mobilealg8367]

@@johnphilipjones thank you very much

[@johnphilipjones]

Woof :-) Phil

[@davidfromstow]

As always, the canine gonads!